The present invention relates to an interface apparatus for a removable RAM package for a data acquisition system, such as an ambulatory blood pressure monitoring system. In particular, the present invention has utility for servicing the RAM package through a standard serial communications link.
A number of portable monitoring devices are used in medical monitoring. One well known device is the so-called Holter monitor which is an EKG monitor which typically uses a magnetic tape recorder to record EKG signals from a patient over extended periods of time. Another is a portable monitor for obtaining blood pressure readings over extended periods of time, such as the Model 5200 ambulatory blood pressure monitor sold by Space-Labs, Inc. of Redmond, WA.
The Model 5200 comprises a blood pressure cuff (described in U.S. Pat. No. 4,206,765), an air pump for activating the blood pressure cuff and a removable RAM package for storing the blood pressure data and timing parameters for controlling automatically when the blood pressure readings are to be taken. The RAM package is described in co-pending U.S. patent application Ser. No. 527,453, filed Aug. 29, 1983, now U.S. Pat. No. 4,592,018 entitled "Removable RAM Package For Ambulatory Medical Monitor". It comprises a RAM and real time timer circuit. The RAM package is detachable from the portable monitor and is inserted into a portable operating system or special adapter for a PC for unloading the blood pressure data.
The RAM has a plurality of data lines and address lines coupled in parallel to an edge connector. The real time timer also has a plurality of data lines coupled to the data lines of the RAM on a common data bus, and address lines coupled to the edge connector. The addressing and data storage and retrieval is done in parallel.
Currently the RAM package is serviced through a unique hardware interface to a personal computer. In order to service the RAM package, a suitable computer with equally suitable interface hardware must be on hand.
The present invention provides means whereby the RAM package can be accessed and serviced through a standard serial interface. A compatible computer need not be on hand, since the servicing can be accomplished remotely through the telephone network using a modem. Thus, the support requirements for servicing a RAM package on site are reduced from a compatible computer with unique interface hardware to an inexpensive interface and an off the shelf modem.